Today's techniques for joining pipes to fittings or valves are mainly based on brass fittings with a conical end and with a nut and a conical clamping ring, where the nut clamps the ring against the taper, which, when the nut is tightened, both form a seal and acts to hold the pipe fixed to the fitting.
Due to deteriorating water quality, low PH and demands for reduced lead content in brass, from the current 2% to 0.2%, the problems caused by stress corrosion increase. The fittings house can rupture at the conical fit, with leaks and thereby water damage as a consequence.
Several years ago regular steel pipes was a good solution, then copper became common, but eventually it turned out that these pipes would not hold more than 20 years. Today metal pipes have been largely replaced with plastic pipes, both inside and outside the house (plumbing and water supply and sewage). Plastic pipes are today recognized as the best and most affordable solution, but it requires other solutions when it comes to fittings and valve connections, for maximum service life and leakage prevention.
There are a significant number of different fitting solutions for such connections. Examples include:
JP410281367 shows an interface where a connector is equipped with an internal groove for an O-ring. A pipe is inserted into the connector and the connector is squeezed against the pipe to lock this in place. This fitting cannot be opened again without cutting the pipe. It is not possible to re-use the connector. It is not possible to use this fitting on a plastic tube, as it will not be possible to attach the plastic tube sufficiently well by squeezing the connector against it.
KR 101273395 shows a fitting of the screw and clamp type, where a pipe end is inserted into the coupling. A nut is arranged around the pipe and screwed to the coupling. A gasket is pressed against the pipe due to a conical surface in the coupling and this clamping action will fixate the tube. It is, however, depending on the nut being screwed sufficiently tight. Too loose tightening may cause leakage. This solution is not suitable for use on plastic pipes unless a support sleeve is used. Even then a leakage may occur.
U.S. Pat. No. 3,393,930 shows a solution where a bead is formed close to the pipe end. This bead is clamped between two fitting elements. A seal seals the connection. This solution requires the use of special tools for making the bead. It is only possible to use metal pipes. The fitting must also be screwed firmly to prevent leakage. The nut must be arranged on the pipe before the forming of the bead. This means that the connection cannot be delivered pre-assembled, and if it is not possible to thread the nut onto the pipe from the other end, the pipe must be produced according to measured length with the nut on the pipe.
CN 202733235 shows an interface, which also has a bead formed close to the tube end. This means that plastic pipes cannot be used. Here too, the fitting has to be screwed firmly to prevent leakage. This solution has the same disadvantages as U.S. Pat. No. 3,393,930.
DE 9308146U also shows a solution in which a bead is formed close to the pipe end. This solution therefore has the same drawbacks as described above.
GB 2129081 describes a solution in which a bead is formed close to the pipe end. The solution is therefore encumbered by the same drawbacks as described above.